Archive for October 2006

Human cells might provide a model for desalination membranes

October 27, 2006

A great model for a desalination membrane is any of the millions of cells we have in our bodies.

Last month NIH funded researchers at the University of Illinois at Urbana-Champaign and the University of Arizona modeled Aquaporins — a class of proteins that form membrane channels in cell walls. Aquaporins allow for water movement between a cell and its surroundings. Researchers found that the same protein can be used as a water channel or an ion channel depending on the signaling pathway activated in the cell.

So what?

If you had an ion gate that could ward off charged sodium ions depending on their charge then you might be able to put one of these gates on a semipermiable membrane and do some serious water desalination–just like human cells do!

The modeling work at Illinois and Arizona builds on models used for the study of ion channel gating kinetics at Los Alamos National Laboratory last year.

This week researchers learned a bit more about the shape of the gate:

Researchers decipher the shape of the sodium/potassium ion pump

Researchers decipher the shape of the sodium/potassium ion pump

Channel surfing. Charged oxygen atoms (red) deep inside a sodium/potassium pump are part of a filter that allows only ions with the correct charge to pass from one side of the cell’s membrane to the other.

Two new papers from Rockefeller University professor David Gadsby, head of the Laboratory of Cardiac and Membrane Physiology, go a long way toward describing the shape of the gated channel in the Na/K pump and providing an understanding of how this pump — and others like it — collects ions on one side and releases them on the other.Many of the residues in an ion pump have an electrical charge that works to either draw in or repel approaching ions, allowing only those with the correct charge to flow through to their destination.

As I mentioned this looks a good model for desalination with carbon nanotubes –if the nanotubes were so large they required gating. Manifest Interconductance Rank (MIR) models and models called Aggregated Markov Processes used for ion gating studies at Los Alamos……. might be adapted for water desalination studies.

GE Global Research’s Hydrogen Electrolyzer

October 20, 2006

This month Popular Mechanics magazine awarded GE Research’s advanced Hydrogen Electrolyzer its 2006 ’s Breakthrough Award.

GE’s electrolyzer, which was developed by a research team at Global Research led by Richard Bourgeois, was recognized for its potential to make hydrogen production by water electrolysis economically feasible. The novel design makes extensive use of GE-developed materials and processes. A GE invented plastic, Noryl™, replaces complex and expensive metal parts. Metal coating techniques from GE’s aircraft engine and power generation products are used to make high performance electrodes with very low processing costs.

So what’s the payoff?

The U.S. Department of Energy has identified electrolyzer capital costs as a major barrier to the competitiveness of hydrogen fuel for transportation. GE’s electrolyzer has the potential to bring the cost of producing hydrogen down to a level that is competitive with the current price of gasoline.

Why did Popular Mechanics think GE’s Hydrogen Electrolyzer was so cool?

“GE’s electrolyzer represents a profound breakthrough in hydrogen energy that has the potential to greatly expand the possibilities in realizing cleaner, more affordable energy solutions, said James Meigs, Editor-in-Chief, Popular Mechanics magazine. “We were impressed as much with the technology’s potential impact as we were with the creativity of design that enabled the breakthrough itself. We applaud GE for this extraordinary achievement.”

Notice that Popular Mechanics mentioned how they were impressed not just by the invention itself but the “creativity of design that enabled the breakthrough itself.” Maybe they used some version of that new autocad tool that allows the the designer to specify the function while the software spits out the form. Or maybe they used some version of that MIT tool that aids cost estimates for complex projects.

“The core issue with producing hydrogen from electrolyzers is that the economics are not there. They are too expensive to build, so we set out in our program to attack the capital costs,“ Fletcher added.

Today, producing hydrogen by water electrolysis costs at least $8 per kg including capital, energy, and operating costs. GE participated in a program with the U.S. Department of Energy that has the goal of bringing the cost to under $3. By lowering costs on the capital side, GE researchers are confident this goal can be met.

So how far along is this new machine?

Thus far, GE researchers have built and tested an electrolyzer big enough to make a kilogram of hydrogen per hour. A kilogram of hydrogen has about the same energy content as a gallon of gasoline.

Where would the electricity come from?

Electrolyzers, when coupled with wind, solar or nuclear power, produce hydrogen from water …..

Or if the system becomes sufficiently efficient–you might use the hydrogen to run an electrical generator to produce more hydrogen with enough hydrogen left over to run something like say…a pump.

The article is thinking that the capital costs are so low the hydrogen electrolyzer could be used for fueling stations .

Within the next decade, electrolyzers could serve as the foundation for future hydrogen vehicle refueling stations.

However, I’m thinking the Hydrogen Electrolyzer could be used for water pumps when you want to pump a lot of fresh water 1000 miles inland. (But again costs and efficiencies will have to decline further to produce surplus energy more cheaply. –And that’s a matter of finding cheaper & better catalysts.)

Redwood Trees

October 13, 2006

Last week’s post mentioned the work of Pittsburgh R.K. Mellon Professor of Chemistry and Physics John T. Yates Jr. He showed that water in carbon nanotube test tubes formed daisy chains connected by hydrogen and then stacked one upon the other as they went into the test tube nanotube.

This was a great puzzlement to me.

After all what did this have to do with the work of the LLNL scientists in May and the work of University of Kentucky scientists last November that showed super fast flow through rates for water passing through carbon nanotubes. (Certainly it seemed that LLNL & UK nanotubes were too wide to stop the Na & Cl atoms .)

What it looked like was that water actually takes on new properties spontaneously so as to conform appropriately to new space.
So I googled carbon nanotube +water and got one of those gee whiz duh wow moments that make science fun.

Consider this two year old post from the American Institute of Physics.

Nanotube Water

Nanotube water, a one-dimensional form of water consisting of a string of water molecules confined in a carbon nanotube, has been studied with neutron scattering by physicists at Argonne National Lab. Neutron scattering measurements, along with computer simulations of the molecular interactions between the water and the surrounding single-walled carbon nanotube, confirmed that water molecules had successfully been taken up into the nanotubes in the form of a “wire.” But this was not all; surrounding the water wire was another water structure, a sheath of water, a cylindrical square-ice- sheet formation (see figure).

The result of this novel architecture was that fluid-like behavior was observed at temperatures far below the freezing point of normal water. The hydrogen bonds along the water chain seem to be softened, allowing, for example, a freer movement of protons along the chain. The Argonne researchers (contact Alexander Kolesnikov,, 630-252-3555) believe that this anomalous behavior might help to explain other phenomena featuring nm-scale confined water such as water migration from soil to plants via xylem vessels and the proton translocation in transmembrane proteins. (Kolesnikov et al., Physical Review Letters, 16 July 2004.)

Might also explain why water goes up a redwood tree. In any case, compare the picture presented by the American Institute of Physics with the picture presented by LLNL in their May 2006 presentation of their carbon nanotube and water experiments.

American Institute of Physics

Nanotube Water

Proposed structure of nanotube-water, water confined with a single-wall carbon nanotube. The interior “chain” water molecules have been colored yellow to distinguish them from the exterior “shell” water molecules in red.

Reported by: Kolesnikov et al., Physical Review Letters, upcoming.

Lawrence Livermore National Laboratory

Methane Molecules Flowing Through Carbon Nanotube
Artist’s rendering of methane molecules flowing through a carbon nanotube less than two nanometers in diameter. (Click here to download a high-resolution image.)

Of course, the LLNL picture shows methane passing through the nanotube and the American Institute of Physics picture shows water passing through the nanotube. But that’s not the point. The point here is that the American Institute of Physics picture may be the more accurate representation of what happened at the LLNL labs. So what? Well, the H20 molecule in Nanotube water has been strung out and shethed in more water. That configuration may be suffiently small & tight to exclude Na & Cl.

Carbon Nanotube Research

October 6, 2006

There’s been a lot of work in carbon nanotubes of late. The work comes from a broad assortment of labs and pushes the nano boundry along a broad front.

Northwestern University has developed a method for making carbon nanotubes in commercial quantities while solving a quality control problem.

Current methods for synthesizing carbon nanotubes produce mixtures of tubes that differ in their diameter and twist. Variations in electronic properties arise from these structural differences, resulting in carbon nanotubes that are unsuitable for most proposed applications.

Now, a new method developed at Northwestern University for sorting single-walled carbon nanotubes promises to overcome this problem. The method works by exploiting subtle differences in the buoyant densities of carbon nanotubes as a function of their size and electronic behavior. The results will be published online Wednesday, Oct. 4, in the inaugural issue of the journal Nature Nanotechnology (October 2006).

The researchers also maintain that their work can be reproduced on an industrial scale.

“The technique is especially promising for commercial applications,” said Hersam, “because large-scale ultracentrifuges have already been developed and shown to be economically viable in the pharmaceutical industry. We anticipate that this precedent can be straightforwardly translated to the production of monodisperse carbon nanotubes.”

Method could help carbon nanotubes become commercially viable

Single-walled carbon nanotubes are coated in soap-like molecules called surfactants, then spun at tens of thousands of rotations per minute in an ultracentrifuge. The resulting density gradient sorts the nanotubes according to diameter, twist and electronic structure. Credit: Zina Deretsky (adapted from Arnold et al.), NSF


In another interesting advance that solves for the carbon nanotube twisting problem MIT researchers have discovered

that certain molecules can attach themselves to metallic carbon nanotubes without interfering with the nanotubes’ exceptional ability to conduct electricity.

Materials scientists tame tricky carbon nanotubes

MIT researchers have discovered that certain molecules can attach themselves to metallic carbon nanotubes without interfering with the nanotubes’ exceptional ability to conduct electricity. At left, the high conductance state has two molecular orbitals, shown in green. Some molecules even let the nanotube switch between highly conductive, left, and poorly conductive (right, with one red molecular orbital), creating the potential for new applications. Image courtesy / Marzari Lab


The work is reported in the Sept. 15 issue of Physical Review Letters.

Carbon nanotubes — cylindrical carbon molecules 50,000 times thinner than a human hair — have properties that make them potentially useful in nanotechnology, electronics, optics and reinforcing composite materials. With an internal bonding structure rivaling that of another well-known form of carbon, diamonds, carbon nanotubes are extraordinarily strong and can be highly efficient electrical conductors.

The problem is working with them. There is no reliable way to arrange the tubes into a circuit, partly because growing them can result in a randomly oriented mess resembling a bowl of spaghetti.

Researchers have attached to the side walls of the tiny tubes chemical molecules that work as “handles” that allow the tubes to be assembled and manipulated. But these molecular bonds also change the tubes’ structure and destroy their conductivity.

Now Young-Su Lee, an MIT graduate student in materials science and engineering, and Nicola Marzari, an associate professor in the same department, have identified a class of chemical molecules that preserve the metallic properties of carbon nanotubes and their near-perfect ability to conduct electricity with little resistance.

Using these molecules as handles, Marzari and Lee said, could overcome fabrication problems and lend the nanotubes new properties for a host of potential applications as detectors, sensors or components in novel optoelectronics.

Attaching a molecule to the sidewall of the tube serves a double purpose: It stops nanotubes from sticking so they can be processed and manipulated more easily, and it allows researchers to control and change the tubes’ electronic properties. Still, most such molecules also destroy the tubes’ conductance because they make the tube structurally more similar to a diamond, which is an insulator, rather than to graphite, a semi-metal.

Some molecular handles can even transform between a bond-broken and a bond-intact state, allowing the nanotubes to act like switches that can be turned on or off in the presence of certain substances or with a laser beam. “This direct control of conductance may lead to novel strategies for the manipulation and assembly of nanotubes in metallic interconnects, or to sensing or imaging devices that respond in real-time to optical or chemical stimuli,” Marzari said.

This approach might help appropriately charge carbon nanotube semi permiable membranes as well for desalination purposes.



Several weeks ago just the most interesting piece of science was done by University of Pittsburgh R.K. Mellon Professor of Chemistry and Physics John T. Yates Jr. I have suggested that the fastest way to get carbon nanotubes to sort out Na and Cl is to dope the nanotubes with impurities that charge the nantubes and therefor variously repel Na or Cl. Professor Yates shows water doing something entirely different.


In collaboration with J. Karl Johnson, who is the William Kepler Whiteford Professor of Chemical Engineering at Pitt, Yates has extensively investigated the use of single-walled carbon nanotubes (SWNTs) as tiny test tubes. SWNTs are cylindrical molecules with a diameter equivalent to about three atoms. The tube walls are made of a single curved sheet of carbon atoms.


Yates and Johnson, along with their students and postdoctoral fellows, obtained a striking result for water molecules confined inside SWNTs, as reported in a recent paper in the Journal of the American Chemical Society. The water molecules inside nanotubes bond together into rings made of seven water molecules. Yates and Johnson, who also are researchers in Pitt’s Gertrude E. and John M. Petersen Institute of NanoScience and Engineering, found that these rings stack like donuts along the nanotube. The rings themselves are bound together by a new type of hydrogen bond that is highly strained compared to the hydrogen bonds within each molecular “donut.”


The researchers first detected this novel hydrogen bond experimentally by its unusual singular vibrational frequency and later deduced its character by modeling. “The behavior of water as a solvent inside of nanotubes will probably differ strongly from its behavior in ordinary water based on the donut configuration and the new kind of hydrogen bond discovered in this work,” says Yates.

In another development, research showed that reactive molecules confined inside nanotubes are well shielded by the nanotube walls from reacting with active chemical species like atomic hydrogen, one of the most aggressive chemical reactants in the chemist’s toolbox. The work suggests that chemists could keep certain molecules from reacting by storing them inside nanotubes, while molecules outside the tube are free to react. “This could provide a new tool for focusing reactive chemistry in the laboratory to select one molecule and exclude another one, tucked away inside of a nanotube,” Yates says.

Yates’ approach to water and carbon nanotubes is pretty neat imho. Someone from the desalination research community needs to approach professor Yates and make him an offer he can’t refuse.

Navier-Stokes Equation Progress?

Penny Smith, a mathematician at Lehigh University, has posted a paper on the arXiv that purports to solve one of the Clay Foundation Millenium problems, the one about the Navier-Stokes Equation. The paper is here, and Christina Sormani has set up a web-page giving some background and exposition of Smith’s work.

Wikipedia describes Navier-Stokes Equations this way:

They are one of the most useful sets of equations because they describe the physics of a large number of phenomena of academic and economic interest. They are used to model weather, ocean currents, water flow in a pipe, motion of stars inside a galaxy, and flow around an airfoil (wing). They are also used in the design of aircraft and cars, the study of blood flow, the design of power stations, the analysis of the effects of pollution, etc. Coupled with Maxwell’s equations they can be used to model and study magnetohydrodynamics.

When these equations pass peer review they’ll be very helpful in algorithms that model fluids in a pipe or maybe even in a carbon nano tube.

One other thing. The Millenium Prize, worth $1 million is working well to advance scientific research.





Frugal Research: Toward Harvesting Research Unknown Unknowns

October 4, 2006

How do you pull in research which embraces research unknown unknowns for water desalination? Set a prize for a bench mark or a goal. For water desalination it might be a prize for desalinising X amount of salt water of Y salt concentrate for Z cost.

Here’s the way they’re thinking about the matter in Hydrogen Research.

Prize Program Set Up to Push Hydrogen-Based Fuel Research

Prize Program Set Up to Push Hydrogen-Based Fuel Research

“Prizes can draw out new ideas from scientists and engineers who may not be willing or able to participate in traditional government research and development programs, while encouraging them, rather than the taxpayer, to assume the risk,” said Science Committee Chairman Sherwood Boehlert, R-N.Y.


Scientists, inventors and entrepreneurs will be able to vie for a grand prize of US$10 million, and smaller prizes reaching millions of dollars, under House-passed legislation to encourage research into hydrogen as an alternative fuel.

Legislation creating the “H-Prize,” modeled after the privately funded Ansari X Prize that resulted last year in the first privately developed manned rocket to reach space twice, passed the House Wednesday on a 416-6 vote. A companion bill is to be introduced in the Senate this week.


Triple Play

“This is an opportunity for a triple play,” said bill sponsor Rep. Bob Inglis, R-S.C., citing benefits to national security from reduced dependence on foreign oil, cleaner air from burning pollution-free hydrogen and new jobs. “If we can reinvent the car, imagine the jobs we can create.”

“Perhaps the greatest role that the H-Prize may serve is in spurring the imagination of our most valuable resource, our youth,” said co-sponsor Rep. Dan Lipinski, D-Ill.

The measure would award four prizes of up to $1 million every other year for technological advances in hydrogen production, storage, distribution and utilization. One prize of up to $4 million would be awarded every second year for the creation of a working hydrogen vehicle prototype.

The grand prize, to be awarded within the next 10 years, would go for breakthrough technology.

“Prizes can draw out new ideas from scientists and engineers who may not be willing or able to participate in traditional government research and development programs, while encouraging them, rather than the taxpayer, to assume the risk,” said Science Committee Chairman Sherwood Boehlert, R-N.Y.

Making Progress

Inglis said the Department of Energy would put together a private foundation to set up guidelines and requirements for the prizes. Anyone can participate, as long as the research is performed in the United States and the person, if employed by the government or a national lab, does the research on his own time.

He said the prize would not take away funds from any federal hydrogen programs, including the $1.7 billion hydrogen research program that President Bush first detailed in 2003.

The Energy Department announced earlier this year that it would provide $119 million in funding for research into hydrogen fuel cells, including $100 million over the next four years to projects to improve components of fuel cell systems.

Several automakers have made advances in hydrogen fuel cell technology or dual gas-hydrogen engines, but such vehicles are still very expensive and there’s no viable infrastructure of fueling stations.